History of the Hundred Years War

The long conflict between France and England, to which historians have given the name of "The Hundred Years' War, " interests us chiefly as an illustration on a great scale of the transition from the mediæval, feudal order of society to the modern, national idea of political organization. Its nearer causes were largely feudal, and its methods were still, to a great extent, those of the earlier period.
Its remoter causes, however, and the motives that kept it alive are to be sought on both sides in a steadily growing sense of national unity and national honor. Under the feudal régime it may fairly be said that it mattered little to the landholding aristocracy whether it were under the sovereignty of one king or another. The thing it really cared about was whether its privileges were such as it had a right to expect, and whether these privileges were likely to be fully and honorably maintained.
So long as this was the case the barons found their profit and their glory in standing by their king in those undertakings which had a certain national character. But if their rights were tampered with, or if another sovereign offered equal guaranties of privilege, they easily took advantage of the flexible feudal arrangements to shift their allegiance...